| Chapter 1: | The New Astronomy |
Moreover, it was plain to see that the sky turns about the Earth as do all planets on average. Because nothing can move of its own accord, Aristotle conceived of a Prime Mover (described in Metaphysics) whose job was to initiate motion in the physical Universe. Aristotle delegated the task of moving the several spheres to lesser deities whose combined effects account for the motion of each of the Ancient Planets. The decreasing gradient of celestial speed matches the decreasing gradient of celestial perfection from Heaven to Earth. Aristotle was supremely confident that he had read the Creator's mind correctly and concluded that the Earth must lie immobile at the center of the Universe.
Aristotle may have written other relevant material that is now lost, but available information indicates that he did not entertain the three rudimentary possibilities that later formed the basis of the New Astronomy. Aristotelians could not believe that they were viewing the celestial drama from a rotating and revolving platform called Earth. They did not separate observed celestial motions into their components because they attributed the motions of objects entirely to the objects themselves, not realizing that they themselves were in motion. Aristotelians thought that what they saw was reality and they made no allowance for the fact that they were located at the center of their own perception. In essence, the tale of the chief cosmological models that developed after Aristotle is one of a steady progression toward the restoration and refinement of Pythagorean principles.
The Geocentric Model
The circles and spheres of divine geometry were useful also because they were much easier to handle mathematically than other figures. Claudius Ptolemy (AD 90–168) made full use of them in his thirteen-volume Almagest (“The Greatest”), which is a comprehensive account of astronomical data and theory extant at the time. Ptolemy followed the prescriptions of Aristotle and later geometricians, notably Hipparchus (c.190–c.120 BC), and applied various geometrical devices ad hoc so that when compounded and with judicious choices of parametric